首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   11330篇
  免费   963篇
  国内免费   575篇
化学   7336篇
晶体学   101篇
力学   481篇
综合类   70篇
数学   1702篇
物理学   3178篇
  2023年   148篇
  2022年   180篇
  2021年   301篇
  2020年   352篇
  2019年   377篇
  2018年   346篇
  2017年   299篇
  2016年   453篇
  2015年   432篇
  2014年   532篇
  2013年   811篇
  2012年   803篇
  2011年   855篇
  2010年   569篇
  2009年   514篇
  2008年   638篇
  2007年   522篇
  2006年   538篇
  2005年   454篇
  2004年   354篇
  2003年   331篇
  2002年   292篇
  2001年   267篇
  2000年   194篇
  1999年   164篇
  1998年   113篇
  1997年   98篇
  1996年   101篇
  1995年   93篇
  1994年   138篇
  1993年   99篇
  1992年   112篇
  1991年   102篇
  1990年   90篇
  1989年   64篇
  1988年   62篇
  1987年   52篇
  1986年   56篇
  1985年   81篇
  1984年   74篇
  1983年   42篇
  1982年   70篇
  1981年   65篇
  1980年   69篇
  1979年   60篇
  1978年   64篇
  1977年   56篇
  1976年   51篇
  1975年   40篇
  1973年   41篇
排序方式: 共有10000条查询结果,搜索用时 265 毫秒
1.
Wang  Xigui  Ruan  Jiafu  Wang  Yongmei  Ji  Shue  An  Siyuan 《Meccanica》2021,56(2):303-316
Meccanica - In gear pair actual alternating meshing process, the comprehensive errors of the transmission system and the thermal elastic deformation of the teeth body cause the gears in the meshing...  相似文献   
2.
Research on Chemical Intermediates - In the process of uranium mining and smelting, large quantities of low-concentration uranium-containing wastewater have been produced. It is an ideal solution...  相似文献   
3.
4.
5.
Computational modeling of the optical characteristics of organic molecules with potential for thermally activated delayed fluorescence (TADF) may assist markedly the development of more efficient emitting materials for organic light-emitting diodes. Recent theoretical studies in this area employ mostly methods from density functional theory (DFT). In order to obtain accurate predictions within this approach, the choice of a proper functional is crucial. In the current study, we focus on testing the performance of a set of DFT functionals for estimation of the excitation and emission energy and the excited singlet-triplet energy gap of three newly synthesized compounds with capacity for TADF. The emitters are designed specifically to enable charge transfer by π-electron conjugation, at the same time possessing high-energy excited triplet states. The functionals chosen for testing are from various groups ranging from gradient-corrected through global hybrids to range-separated ones. The results show that the monitored optical properties are especially sensitive to how the long-range part of the exchange energy is treated within the functional. The accurate functional should also be able to provide well balanced distribution of the π-electrons among the molecular fragments. Global hybrids with moderate (less than 0.4) share of exact exchange (B3LYP, PBE0) and the meta-GGA HSE06 are outlined as the best performing methods for the systems under study. They can predict all important optical parameters correctly, both qualitatively and quantitatively.  相似文献   
6.
Russian Physics Journal - The double coaxial resonator with a shortening capacitance is calculated by the partial volume method. The double resonator is represented by two single coaxial resonators...  相似文献   
7.
尚坤  高艺欣  赵乐  王力彬  岳昌武 《合成化学》2022,30(10):819-826
以1,4-二溴-2,5-二甲基苯和4-吡啶硼酸为原料,经两步合成了一种新颖的含吡啶基团的二羧酸配体。通过核磁共振氢谱及傅里叶变换红外光谱对配体结构进行表征,通过热重分析对配体的热稳定性进行了测试;通过溶剂热法对配体的单晶进行培养,并考察反应温度、时间、pH和溶剂等条件对单晶培养的影响。结果表明:在反应温度为80 ℃,反应时间为12 h、溶剂为蒸馏水、溶液pH=5的条件下可获得高质量单晶。该配体为单斜晶系,属于C2/c空间群,结构中含有4个氧原子和2个氮原子,可为金属离子的配位提供足够的位点,有望应用于配合物的设计或催化、吸附和医药载体等行业。  相似文献   
8.
9.
Ma  Zongcheng  Hu  Junhua  Feng  Jinfu  Liu  An  Chen  Guoming 《Nonlinear dynamics》2020,99(2):1195-1210
Nonlinear Dynamics - A trans-media aerial underwater vehicle (TMAUV) could break through the single-medium limitation with the abilities to fly in the air, navigate underwater, and cross the...  相似文献   
10.
In this work,(-201) β-Ga_2O_3 films are grown on GaN substrate by metal organic chemical vapor deposition(MOCVD). It is revealed that the β-Ga_2O_3 film grown on GaN possesses superior crystal quality, material homogeneity and surface morphology than the results of common heteroepitaxial β-Ga_2O_3 film based on sapphire substrate. Further, the relevance between the crystal quality of epitaxial β-Ga_2O_3 film and the β-Ga_2O_3/GaN interface behavior is investigated. Transmission electron microscopy result indicates that the interface atom refactoring phenomenon is beneficial to relieve the mismatch strain and improve the crystal quality of subsequent β-Ga_2O_3 film. Moreover, the energy band structure of β-Ga_2O_3/GaN heterostructure grown by MOCVD is investigated by X-ray photoelectron spectroscopy and a large conduction band offset of 0.89 eV is obtained. The results in this work not only convincingly demonstrate the advantages of β-Ga_2O_3 films grown on GaN substrate, but also show the great application potential of MOCVD β-Ga_2O_3/GaN heterostructures in microelectronic applications.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号